This month starts with us relaxing our clocks back into a more natural rhythm with the Earth’s diurnal cycle, as we conclude Daily Saving Time the first Sunday of November and fall back one hour to Standard Time. This means our evenings get darker sooner, and the stars come out earlier for sky-watchers. It also means clock noon and solar noon once again roughly coincide. With evening arriving earlier, this month we’ll continue our series of looking more closely at sky objects that can be seen through sidewalk telescopes even from the streets and backyards of Kankakee.
The bright planets are still mostly grouped in the pre-dawn sky, but evening begins with the constellation Cassiopeia high in the northern sky. This recognizable, easy-to-find constellation hosts a pair of impressive multiple-star systems. Nearby are some lovely clusters and the famous Andromeda Galaxy (often unfortunately washed out by the light pollution in the skies above town).
Cassiopeia is shaped by turns as a 3, a W, an E, or an M depending on its orientation in the northern skies. In the early evening skies of November, it looks like an angular number 3, its bottom pointed down toward the northeast, with five bright stars marking the ends and each angle of its zig-zag shape.
To find our first double star, η (eta) Cassiopeiae, look for a fairly bright star halfway down the second “zag” of the zig-zag number three. This star is one of the most famous binary stars of the night sky. Though it looks like a single star, through a telescope it’s revealed as two stars—a bright yellowish star with a dimmer, reddish companion nearby. Measures of the relative positions of these stars over decades have revealed that this system is actually gravitationally bound, with an orbital period of about five hundred years. The system itself is about 20 light years away, but the two component stars are separated from each other by a distance of only 70 times the distance between the Earth and the Sun,
Once you’ve tried your hand at finding and viewing η Cassiopeiae, the next target in Cassiopeia is ι (iota) Cassiopeiae, a moderately bright star just below the constellation’s southernmost “zag.” Drawing a line through the southernmost two stars of Cassiopeia’s zig-zag, extending again about as far as the distance between the stars, will get you there. Through a telescope, ι Cassiopeiae will look like a smaller version of η Cassiopeiae. In fact though, it’s not a double but a triple system, with the brighter component actually itself a very close double star. Under high magnification and clear viewing, you may be able to just barely spot a small blue companion close to the yellow primary star. This entire triple system is about 160 light years from Earth.
If we go east from the bottom of Cassiopeia, toward the constellation Perseus, we’ll run into the Double Cluster (NGC 869 and 884). Visible with the naked eye in dark skies, these have to be “felt out” in brighter city skies. Once spotted though, they’re still an impressive sight. They are best viewed at lowest magnification in the telescope (or even with a pair of binoculars) and are examples of open or galactic clusters, composed of hundreds of young (six to twelve million years old) stars seven thousand to eight thousand light years away. In the telescope eyepiece they fill the view with dozens of bright, crowded stars.
Now, leaving the best for last (and omitting the fabulous Andromeda Galaxy which is nearby but washed out in city skies), we move to Almach, also known as γ (gamma) Andromedae, to the southeast of Cassiopeia, marking one of the feet of the constellation Andromeda. Almach is one of the most impressive double stars in the sky. Its component stars are a bit closer together than those of η Cassiopeiae but they have a brilliant, sharp color contrast between the yellow/gold primary and the dimmer blue companion star. Like ι Cassiopeiae though, one of the components of Almach (the dimmer blue star) is itself a close double as well, though I have not been able to separate these components in my backyard telescope. It doesn’t stop there though: one of those stars is in addition an even closer binary star with a period of only three days, making the whole system actually a quadruple star system.
I occasionally hear that the early evenings of autumn make people feel winter is finally here and sometimes even lead to seasonal doldrums. I maintain though that darker, earlier evenings are a fantastic opportunity to get out and learn about the dynamic, tangled lives of those bright stars above us. Hopefully these objects give you a place to start!
This column appeared first in the Kankakee Daily Journal.